The invention relates to improvements in socalled counterpressure type container filling apparatus. More particularly, the invention relates to improvements in apparatus of the type disclosed in commonly owned copending patent application Ser. No. 07/568,273 filed Aug. 15, 1990 by Manfred Mette for "Apparatus for filling bottles and the like", in commonly owned copending patent application Ser. No. 07/675,428 filed Mar. 26, 1991 by Jacek Walusiak for "Apparatus for admitting metered quantities of liquid into bottles or other containers", and in commonly owned copending patent application Ser. No. 07/687,453 filed Apr. 18, 1991 by Manfred Mette for "Apparatus for filling bottles with a liquid".
Apparatus of the character to which the present invention pertains employ so-called container centering and sealing units which are mounted at the underside of a preferably rotary vessel or tank for a supply of liquid to be dispensed and for a supply of a compressed gaseous fluid, such as carbon dioxide gas. The vessel has outlets, one for each combined centering and sealing unit, to discharge metered quantities of liquid into containers while the open tops of such containers are properly engaged by the respective units. Gas conveying conduits are provided to admit compressed gas into the containers prior to admission of a liquid (such as a carbonated beverage) and to permit evacuation of gas from containers in the course of the filling step. The mode of operation is preferably such that the pressure in a container (such as a bottle or a can) can be maintained above atmospheric pressure upon completion of the filling step. As a rule, the combined centering and sealing units are installed at the underside or around the circumference of a tank which is indexible or is continuously rotatable about a substantially vertical axis and confines a supply of pressurized liquid, normally a body of liquid beneath a cushion of compressed gas. The manner in which the conduits are connected with the tank so that they can receive compressed gas from or can admit compressed gas into the aforementioned cushion is described in the above-identified copending applications to which reference may be had, if necessary. The flow of gaseous fluid in the conduits is or can be controlled by suitable valves.
Each combined centering and sealing unit is or can be provided with, or can be connected to, a liquid metering chamber and can carry or cooperates with various moving, actuating, sealing and/or other devices which become operative during selected stages of each container filling operation.
The centering operation can be carried out by tulip-shaped centering elements which engage the open tops of containers to be filled with a liquid and seal the open tops from the atmosphere in the course of the pressurizing and filling steps. The centering elements can constitute fixedly mounted parts of the respective combined centering and sealing units; this can be seen by referring, for example, to published German patent application No. 37 17 256. A container to be filled is lifted from below toward engagement with the stationary centering element of the respective combined sealing and centering unit and is pressed against a washer or another sealing element with a force which suffices to ensure adequate sealing of the container from the atmosphere until after completion of the filling operation. It is also known to lower the centering element onto the open top of a container below it, i.e., while the level of the empty container remains at least substantially unchanged. Each combined sealing and centering unit then comprises means for raising and lowering the respective centering element which latter is mounted on the casing of the respective unit. A drawback of those apparatus which employ vertically movable centering elements is that each unit must be provided with seals which are engaged by mobile parts so that the wear upon the seals is extensive, especially if such seals are utilized in the combined centering and sealing units of a modern container filling apparatus which is designed to fill large or very large numbers of containers per unit of time. Another drawback of such apparatus is that the cost of each combined centering and sealing unit is very high, and this is attributable in part to the need for accurate guide means which serve to confine the mobile centering element of each unit to reciprocatory movements along accurately determined paths, i.e., with a minimum of stray movement.
A drawback which is common to all presently known container filling apparatus of the above outlined character is that it is difficult to gain access to the centering and/or other elements or components of the combined centering and sealing units. Thus, it is necessary to dismantle the apparatus whenever the operators decide that the aforementioned units or certain parts of such units require a thorough cleaning or rinsing, e.g., prior to conversion of the apparatus for the filling of containers with a different liquid. Since a modern container filling apparatus normally comprises a very large number of combined centering and sealing units, even a partial dismantling of each such unit prior to a cleaning operation and reassembly of such units upon completion of a cleaning operation takes up much time with attendant considerable losses in output. In many instances, dismantling and reassembly of combined centering and sealing units must be carried out by skilled workers.